Methods and Apparatus For Treating Spinal Stenosis

ABSTRACT

This invention relates generally to spine surgery and, in particular, to methods and apparatus for treating spinal stenosis with a spinous process spacer and an overlay designed to extend between the superior and inferior spinous processes in order to restore the integrity and functional benefits of the supraspinous ligament.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/635,698 filed Dec. 6, 2006, now U.S. Pat. No. 7,862,592 which claimsthe benefit under 35 U.S.C. §119(e) to U.S. Provisional Application Ser.No. 60/748,107 filed Dec. 6, 2005, the entire contents of which arehereby expressly incorporated by reference into this disclosure as ifset forth fully herein.

BACKGROUND OF THE INVENTION

I. Field of the Invention

This invention relates generally to spine surgery and, in particular, tomethods and apparatus for treating spinal stenosis.

II. Discussion of the Prior Art

Spinal stenosis is a narrowing of spaces in the spine which results inpressure on the spinal cord and/or nerve roots. This disorder usuallyinvolves the narrowing of one or more of the following: (1) the canal inthe center of the vertebral column through which the spinal cord andnerve roots run, (2) the canals at the base or roots of nerves branchingout from the spinal cord, or (3) the openings between vertebrae throughwhich nerves leave the spine and go to other parts of the body.

Pressure on the lower part of the spinal cord, or on nerve rootsbranching out from that area, may give rise to pain or numbness in thelegs. Pressure on the upper part of the spinal cord (neck area) mayproduce similar symptoms in the shoulders, or even the legs. Thecondition generally occurs in patients who are in their last decade ordecades of life.

Laminectomy, which involves removing bone, the lamina, from thevertebrae, is the most common surgical treatment for spinal stenosis.Laminectomy enlarges the spinal canal, thus relieving the pressure oncompressed nerves. Surgical burs, drills, punches, and chisels are usedduring the procedure.

Surgeons risk injuring the nerves or the spinal cord as they enlarge thespinal canal. In addition, elderly patients frequently haveco-morbidities that increase the risk of laminectomy.

Complications of laminectomy include increased back pain, infection,nerve injury, blood clots, paralysis, prolonged recovery, and death.

Lumbar fusion is frequently preformed in conjunction with laminectomy.Current fusion techniques require abrasion of large surfaces of bone.Bone bleeds during and after abrasion. Current fusion techniquesincrease the risk of spinal stenosis procedures. Fusion also prolongspatient recovery following spinal stenosis surgery. Furthermore, variousfusion techniques require the severing and/or removal of certain softtissue surrounding the spine, including but not limited to thesupraspinous ligament, the intraspinous ligament, the ligamentum flavum,the posterior longitudinal ligament, and/or the anterior longitudinalligament.

Increasingly, surgeons are looking for improved methods of effectingless invasive treatments for spinal stenosis. The device must be able tobe safely and consistently implanted without excess damage to thepatient. The present invention is directed at overcoming, or at leastimproving upon, the disadvantages of the prior art.

SUMMARY OF THE INVENTION

This invention is directed to a surgical apparatus for treating spinalstenosis without the need for a laminectomy. Broadly, the inventionresides in an apparatus configured for placement in an intraspinousspace, (e.g. posteriorly to a spinal canal between a first spinousprocess and an adjacent second spinous process). In the preferredembodiment, the device permits spinal flexion while limiting spinalextension, thereby providing an effective treatment for treating spinalstenosis. The invention may be used in the cervical, thoracic, or lumbarspine.

The preferred embodiments teach a spinal apparatus configured forplacement between adjacent vertebrae and adapted to fuse to a firstspinous process. Various mechanisms, including shape, porosity, tethers,and bone-growth promoting substances may be used to enhance fusion. Thetether may be a wire, cable, suture, allograft tissue, or other singleor multi-filament member. Preferably, the device forms a pseudo-joint inconjunction with the non-fused vertebra.

The spinous process spacer of the present invention may be of bone ornon-bone construction. In the bone embodiments, the spinous processspacer may be constructed from any suitable allograft, including but notlimited to portions of clavicle, rib, humerus, radius, ulna, metacarpal,phalanx, femur, tibia, fibula, or metatarsal bone. In non-boneembodiments, the spinous process spacer may be any suitableconstruction, including but not limited to polyaryletherketone (PEEK)and/or polyaryletherketoneketone (PEKK). In either event, the spacerincludes a slot or indent to receive a portion of a spinous process toenhance fusion. The device may contain one or more bone-growth promotingsubstances such as BMP1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 . .. n, demineralized bone matrix, allograft cancellous bone, autograftbone, hydroxyapatite, coral and/or other highly porous substance.

During insertion of the spinous process spacer of the present invention,it may become necessary to sever the supraspinous and interspinousligaments. In such instances it may be desirable to include an overlaydesigned to extend from one of the first and second spinous processes tothe other in order to restore the integrity and functional benefits ofthe supraspinous and/or intraspinous ligaments.

BRIEF DESCRIPTION OF THE DRAWINGS

Many advantages of the present invention will be apparent to thoseskilled in the art with a reading of this specification in conjunctionwith the attached drawings, wherein like reference numerals are appliedto like elements and wherein:

FIG. 1 is a side view of the spinous processes of a pair of adjacentvertebrae with a spinous process spacer according to one embodiment ofthe present invention inserted therebetween, illustrating in particularthe spinous process spacer tethered to one spinous process during use;

FIG. 2 is a perspective view of the spinal process spacer assembly ofFIG. 1 including bone growth promoting material;

FIG. 3 is a perspective view of a spinous process spacer according toone embodiment of the present invention;

FIG. 4 is a side plan view of the spinous process spacer of FIG. 3;

FIG. 5 is a front plan view of the spinous process spacer of FIG. 3;

FIG. 6 is a top plan view of the spinous process spacer of FIG. 3;

FIG. 7 is a front cross section view of the spacer of FIG. 3;

FIG. 8 is a perspective view of a spinous process spacer according to analternative embodiment of the present invention;

FIG. 9 is a side view of the spinous process spacer of FIG. 8;

FIG. 10 is an end view of the spinous process spacer of FIG. 8;

FIG. 11 is a side view of the spinous processes of a pair of adjacentvertebrae with a spinous process spacer according to one embodiment ofthe present invention inserted therebetween, illustrating the spinousprocess spacer thethered to one spinous process during use and furtherillustrating the disruption of the supraspinous ligament and theintraspinous ligament during insertion;

FIG. 12 is a side view of the affixed spinous process spacer of FIG. 11,illustrating the further use of an overlay spanning from one spinousprocess to the other, primarily covering the distal portions of thespinous processes; and

FIG. 13 is a side view of the affixed spinous process spacer of FIG. 11,illustrating the further use of an overlay spanning from one spinousprocess to the other and covering a significant portion of the spinousprocesses.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Illustrative embodiments of the invention are described below. In theinterest of clarity, not all features of an actual implementation aredescribed in this specification. It will of course be appreciated thatin the development of any such actual embodiment, numerousimplementation-specific decisions must be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, which will vary from one implementation toanother. Moreover, it will be appreciated that such a development effortmight be complex and time-consuming, but would nevertheless be a routineundertaking for those of ordinary skill in the art having the benefit ofthis disclosure. The spinal alignment system disclosed herein boasts avariety of inventive features and components that warrant patentprotection, both individually and in combination.

FIG. 1 illustrates a perspective view of a spinous process spacer(“SPS”) assembly 10 of the present invention in use between the spinousprocesses of a pair of adjacent vertebrae in a human spine. The SPSassembly 10 includes a spacer 12, a primary tether 14, and two sidetethers 15 (only one of which is shown in FIG. 1). The spacer 12, asillustrated in FIGS. 4-8, is generally cylindrical and includes a mainchamber 16, a pair of insertion tool apertures 18, a fusion notch 20,and a pair of tether lumens 22. As will be described in greater detailbelow, according to a preferred embodiment the spacer 12 is coupled toonly one spinous process (e.g. the superior spinous process 2 as shownin FIG. 1). This is accomplished, by way of example only, by securingthe primary tether 14 to the superior spinous process 2 (as a first stepof affixation), and then using a pair of side tethers 15 to affix spacer12 to the primary tether 14. This step may be accomplished, by way ofexample only, by passing one side tether 15 through each of the tetherlumens 22, further passing the side tether 15 between the superiorspinous process 2 and the primary tether 14, and finally tightening eachside tether 15 until the spacer 12 is generally transverse to thelongitudinal axis of the spine.

The spacer 12 may be of bone or non-bone construction. The boneembodiment involves manufacturing the spacer 12 from a suitableallograft, including but not limited to clavicle, rib, humerus, radius,ulna, metacarpal, phalanx, femur, tibia, fibula, or metatarsal bone. Thenon-bone embodiment involves manufacturing the spacer 12 from suitablenon-bone materials, including but not limited to polyaryletherketone(PEEK) and polyaryletherketoneketone (PEKK). In either event, the spacer12 is designed to fuse to the superior spinous process 2 over time,resulting in what is called “hemi-fusion” in that the spacer 12 will befused to only one spinous process. This may be augmented by disposingany number of suitable fusion-inducing materials 17 within the spacer 12(as shown by way of example only in FIG. 2), including but not limitedto BMP1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 . . . n,demineralized bone matrix, allograft cancellous bone, autograft bone,hydroxyapatite, coral and/or other highly porous substance.

Although shown and described with regard to the superior spinous process2, it will be appreciated that the spacer 12 may also be coupled to onlythe inferior spinous process 4 without departing from the scope of thepresent invention. The spacer 12, once positioned, serves to distractthe interspinous process space, which advantageously restores foraminalheight in stenotic patients and may also indirectly decompress theintervertebral space.

As depicted in FIGS. 3-4, the main chamber 16 extends through thelateral sides of the spacer 12. The main chamber 16 may be provided inany of a variety of suitable shapes in addition to the generallycylindrical shape as shown, including but not limited to a generallyoblong, triangular, rectangular shape and/or combinations thereof. Thepair of insertion tool apertures 18 may be located on either theposterior or anterior side of the spacer 12 and extend a portion of theway through the spacer 12. The fusion notch 20 includes a slot or indentto receive a portion of the superior spinous process 2 (or othervertebral structure) to enhance fusion. The fusion notch 20 may belocated generally towards the middle portion of the top of the spacer12. The notch 20 helps center the spacer 12 relative to the superiorspinous process.

As best shown in FIG. 7, the tether lumens 22 each extend at an anglethrough the top surface of the spacer 12 and into the main chamber 16.Each tether lumen 22 may be provided in any of a variety of suitableshapes in addition to the cylindrical shape shown, including but notlimited to oblong, triangular, rectangular and/or any combinationthereof. The primary tether 14 and the side tethers 15 may comprise anynumber of suitable materials and configurations, including but notlimited to wire, cable, suture thread (permanent and/or bioresorbable),allograft tissue and/or other single or multi-filament member. Suturethread may include any number of components capable of attaching to aspinous process, including but not limited to ordinary suture threadsknown to and used by those skilled in the art of wound closure. Thetethers 14, 15 may be of any length necessary to effectively fuse thespacer 12 to the particular spinous process.

According to an alternative embodiment of the present invention shown inFIGS. 8-10, the spacer 12 may be provided with a second notch 21opposite the fusion notch 20. The second notch 21 is capable of restingon the inferior spinous process 4 during use, which may assist inmaintaining the spacer 12 in a fully centered position relative to theinferior spinous process 4. As best shown in FIG. 8, the fusion notch 20may be further provided with slots 23 extending into the main chamber16. When the spacer 12 is coupled to the superior spinous process 2,these slots 23 will establish direct communication between thefusion-inducing compounds provided within the main chamber 16 and thelower aspect of the superior spinous process 2, which advantageouslyaugments the ability of the spacer 12 to fuse to the superior spinousprocess 2 (particularly if the spacer 12 is constructed of non-bonematerials).

During insertion of the spinous process spacer of the present invention,it may become necessary to sever the supraspinous and interspinousligaments. FIG. 11 illustrates a SPS assembly 10 attached to a superiorspinous process 2 as described above. Supraspinous ligament 6 isillustrated having been severed during the insertion process.Intraspinous ligaments 7, 9 remain intact, while intraspinous ligament 8(situated between superior spinous process 2 and inferior spinousprocess 4) is also severed.

FIG. 12 illustrates an alternative embodiment of the present invention,in which the SPS assembly 10 may further include an overlay 30 designedto extend between the superior and inferior spinous processes 2, 4 inorder to restore the integrity and functional benefits of thesupraspinous ligament 6. By way of example only, overlay 30 may be anymaterial suitable for restoring the structural and functional integrityof the supraspinous ligament 6, including but not limited to a surgicalmesh, textile, and/or embroidery. Exemplary textiles are shown anddescribed in commonly owned U.S. Pat. No. 5,990,378 entitled “TextileSurgical Implants Anchors,” which is attached hereto as Exhibit Aforming part of this disclosure, and commonly owned US PatentApplication Publication No. 2004/0078089 entitled “Textile Prosthesis,”which is attached hereto as Exhibit B forming part of this disclosure.Anchors 32 may be used to secure the overlay 30 to the spinous processes2, 4. Preferably, anchors 32 are inserted into the distal portion of thespinous processes 2, 4, however it is contemplated that anchors 32 maybe inserted into any portion of the spinous process suitable to providepurchase. Optionally, side anchors 34 may be inserted into the side ofthe spinous processes 2, 4 to further secure the overlay 30 to the bone.Anchors 32 and side anchors 34 may be any device suitable for attachingthe overlay 30 to the bone, including but not limited to pins, screws,nails, tacks, staples, and the like.

FIG. 13 illustrates a still further alternative embodiment of thepresent invention, in which the SPS assembly 10 may further include anoverlay 36 designed to extend between the superior and inferior spinousprocesses 2, 4 in order to restore the integrity and functional benefitsof the supraspinous ligament 6 and the intraspinous ligament 8. By wayof example only, overlay 36 may be any material suitable for restoringthe structural and functional integrity of the supraspinous ligament 6,including but not limited to a surgical mesh, textiles, and/orembroidery (including the exemplary textiles referenced above). Anchors38 may be used to secure the overlay 30 to the spinous processes 2, 4.Preferably, anchors 38 are inserted into the distal portion of thespinous process spacers 2, 4, however it is contemplated that anchors 38may be inserted into any portion of the spinous process suitable toprovide purchase. Optionally, side anchors 40 may be inserted into theside of the spinous processes 2, 4 to further secure the overlay 36 tothe bone. Anchors 38 and side anchors 40 may be any device suitable forattaching the overlay 36 to the bone, including but not limited to pins,screws, nails, tacks, staples, and the like.

Although shown as separate components, it is contemplated that overlays30, 36 may be integrally formed with spacer 12 such that the overlay andspacer are inserted contemporaneously.

The spacer 12 according to the present invention may be constructed ofallograft bone and formed in a generally cylindrical shape. The spacer12 of the present invention may be provided in any number of suitableshapes and sizes depending upon a particular patient and the shape andstrength characteristics given the variation from cadaver to cadaver.The spacer 12 may be dimensioned for use in the cervical and/or lumbarspine without departing from the scope of the present invention. Thespacer 12 may be dimensioned, by way of example only, having a lengthranging between 6-20 mm and a height ranging between 20-25 mm.

The SPS assembly 10 of the present invention may be introduced into aspinal target site through the use of any of a variety of suitableinstruments having the capability to releasably engage the spacer 12. Ina preferred embodiment, the insertion tool permits quick, direct,accurate placement of the spacer 12 between an upper and lower spinousprocess. An exemplary insertion tool is shown and described in commonlyowned U.S. Pat. No. 6,923,814 entitled “System and Method for CervicalFusion,” which is attached hereto as Exhibit C forming part of thisdisclosure.

In order to use the SPS assembly 10 of the present invention in atreatment of spinal stenosis, a clinician must first designate theappropriate spacer size 12. A clinician can utilize the SPS assembly 10in either an open or minimally invasive spinal fusion procedure. Ineither type of procedure, a working channel would be created in apatient that reaches a targeted spinal level. After the creation of theworking channel, the interspinous space would be prepared. Afterpreparation a sizer instrument is used to determine the appropriate sizeof the spacer 12. Then the spacer 12 is positioned and inserted into theprepared space between the spinous processes. The device forces thespinous processes apart. The spine flexes as the spinous processes areforced apart. The neuroforamina and the spinal canal are enlarged as thespine is flexed. The SPS assembly 10 holds the vertebrae in a flexedposition. By way of example only, the SPS assembly 10 may be made froman allograft shaft of a long bone such as the humerus, tibia, fibula,radius, ulna, or femur.

Preparation of the inter spinous process space includes perforating theinterspinous ligament between the superior and inferior spinousprocesses. The supraspinous ligament may be either severed or leftintact and distracted out of the way if necessary. A key part of thepreparation includes abrading the inferior portion of the superiorspinous process where it will communicate with the fusion inducingmaterials 32 packed in the main chamber 16. Abrading removes the hardcortical bone from the inferior surface of the superior spinous processand leaves bleeding bone which is better adapted for fusion. As new bonegenerates to heal the abraded portion it may grow into the main chamber16, fixing spacer 12 to the superior spinous process. In the event thatthe supraspinous ligament has been severed, it may be desirable tosecure an overlay 36 to the superior and inferior spinous processes asdescribed above.

When constructed from allograft, the spacer 12 may be manufacturedaccording to the following exemplary method. If necessary, first use abelt sander to reduce any high spots or imperfections to standardize theshape of the bone. Cut the allograft bone to length using the band saw.Remove the cancellous material from the inner canal to create the mainchamber 16. Using calipers, measure the struts and create a sizedistribution of spacers 12. Machine the insertion tool apertures 18.Set-up a standard vice for holding the implant across its width on themill. Use a 3/32″ ball end mill to create the insertion tool apertures18 (same as cervical allograft implant). Insert the spacer 12 into thevice and tighten. Calculate the centerline of the 20 or 25 mm longspacer 12. Create the holes 2.26 mm away from each side of thecenterline (4.52 mm hole to hole distance). Create a notch 22 for thespinous process. Set-up the cervical allograft holding fixture that usesthe insertion tool apertures 18 and vice to hold the spacer 12 acrossits width on the mill. Use a ¼″ flat end mill to create the notch 22.Calculate the centerline of the 20 or 25 mm long spacer 12. Insert thespacer 12 onto the fixture using the insertion tool apertures 18 andtighten the vice. This automatically verifies the correct sizing/spacingof the insertion tool apertures 18. Measure the spacer 12 height.Calculate the cut depth to create the desired spacer 12 size. Cut theflat on the spacer 12 to the desired depth. Remeasure the spacer 12 toinsure proper cut depth. Drill the angled lumens 22 in face of spacer12. Remove the spacer 12 from the cervical allograft fixture and tighteninto the standard vice. Using a battery powered or corded drill with a1/16″ drill bit, drill through the front face to the canal on bothsides. Belt sand the face if needed to create a flat surface for thedrill bit to engage the spacer 12.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof have been shown by wayof example in the drawings and are herein described in detail. It shouldbe understood, however, that the description herein of specificembodiments is not intended to limit the invention to the particularforms disclosed, but on the contrary, the invention is to cover allmodifications, equivalents, and alternatives falling within the spiritand scope of the invention as defined herein.

1. A system for treating spinal stenosis, comprising: an implantdimensioned to fit between a superior spinous process and an inferiorspinous process, the implant including a first notch to receive thesuperior spinous process and a second notch to receive the inferiorspinous process to effect fusion between at least one of the first notchand the superior spinous process and the second notch and the inferiorspinous process; and an overlay dimensioned to extend from a distalportion of the first spinous process to a distal portion of the secondspinous process to restore the supraspinous ligament.
 2. The system ofclaim 1, further comprising a coupling element configured to maintainplacement of the implant between the superior spinous process and theinferior spinous process;
 3. The system of claim 1, wherein the implantis made of at least one of a bone material and a non-bone material. 4.The system of claim 3, wherein the non-bone material is at least one ofpolyetheretherketone and polyetherketoneketone.
 5. The system of claim1, wherein the overlay comprises at least one of surgical mesh, textileand embroidery.
 6. The system of claim 1, further comprising a pluralityof anchors to secure the overlay to the superior spinous process and theinferior spinous process.
 7. The system of claim 6, wherein the anchorsinclude at least one of pins, screws, nails, tacks and staples.
 8. Thesystem of claim 1, wherein the overlay extends over a portion of thesides of the superior spinous process and over a portion of the sides ofthe inferior spinous process such that the implant is covered by theoverlay.
 9. The system of claim 1, wherein the overlay is formed as anintegral part of the implant.
 10. A method for treating spinal stenosis,comprising: gaining access to an interspinous space between a firstspinous process and a second spinous process; inserting an implant inthe interspinous space, the implant dimensioned to fit between the firstspinous process and the second spinous process, the implant including afirst notch to receive the first spinous process and a second notch toreceive the second spinous process to effect fusion between at least oneof the first notch and the first spinous process and the second notchand the second spinous process; and securing an overlay to at least aportion of the first spinous process and at least a portion of thesecond spinous process such that the overlay extends from a distalportion of the first spinous process to a distal portion of the secondspinous process to restore the supraspinous ligament.
 11. The method ofclaim 10, wherein the overlay comprises at least one of surgical mesh,textile and embroidery.
 12. The method of claim 10, wherein securing theoverlay comprises introducing at least one anchor into each of the firstand second spinous processes and through the overlay.
 13. The method ofclaim 12, wherein the anchors include at least one of pins, screws,nails, tacks and staples.
 14. The method of claim 10, wherein theoverlay extends over a portion of the sides of the first spinous processand over a portion of the sides of the second spinous process such thatthe implant is covered by the overlay.
 15. The method of claim 10,wherein the overlay is formed as an integral part of the implant. 16.The method of claim 10, further comprising abrading a portion of atleast one of the first spinous process or second spinous process. 17.The method of claim 10, further comprising applying fusion inducingmaterials in contact with the implant to effect fusion between theimplant and at least one of the first spinous process and the secondspinous process
 18. The method of claim 17, wherein the fusion inducingmaterial includes any of Bone Morphogenic Protein, demineralized bonematrix, allograft cancellous bone, autograft bone, hydroxyapatite andcoral.
 19. The method of claim 10, further comprising coupling theimplant between the first spinous process and the second spinous processwith a coupling element to maintain placement of the implant.
 20. Themethod of claim 10, wherein the implant is made of at least one of abone material and a non-bone material.
 21. The method of claim 20,wherein the non-bone material is at least one of polyetheretherketoneand polyetherketoneketone.